This invention relates to improvements in audio loudspeakers, especially for multimedia applications.
Audio loudspeakers are a common way to transduce an electrical signal into sound waves. The audio loudspeaker accepts an electrical signal from an external source and moves a sound driver surface, such as a speaker cone, to produce sound waves. Such audio loudspeakers have been widely used in audio, computer, medical, manufacturing and other fields. However, as these loudspeakers are called upon to perform more demanding roles in advancing technology, such as in computer multimedia, home entertainment and other varied technologies, their shortcomings have become evident.
FIG. 1A is an illustration of a prior art cone loudspeaker. In FIG. 1A, loudspeaker 100 is shown in a cutaway view with primary functional components, namely voice coil former 10, voice coil 12, ferrite magnet 14 and copolymer cone 16, being visible. In operation, an electrical signal is first applied to the voice coil 12. This voice coil 12 is typically a single strand of wire wrapped many times around coil former 10. Since voice coil 12 resides close to ferrite magnet 14, voice coil 12 is immersed in a magnetic field created by the ferrite magnet 14. As electricity flows through the voice coil 12, a magnetic field is created which interacts with the permanent magnetic field of the ferrite magnet 14. This interaction between the magnetic fields of the voice coil 12 and the ferrite magnet 14 creates movement of the attached cone 16 proportional to the current flowing through the voice coil 12.
FIG. 1B shows a side cutaway view of another cone loudspeaker of the prior art. FIG. 1B shows some of the same primary components of FIG. 1A, such as voice coil 12, magnet 14 and cone 16. In FIG. 1B, though, an external source providing an electrical signal is connected to contacts 20 and through leads 18 in order to drive the loudspeaker.
FIG. 1C shows an enlarged view of voice coil former 10 and voice coil 12 in another prior art cone loudspeaker, along with leads 18.
While the prior art cone loudspeaker of FIGS. 1A, 1B and 1C has been adequate to reproduce analog sound from a single source, the prior art cone loudspeaker suffers from several deficiencies, especially when called upon to perform in high-quality computer or multimedia applications. For example, the prior art cone loudspeaker has only a single voice coil wire so that it can only receive only a single signal from a single external signal source. This feature makes the prior art cone loudspeaker a single function (i.e., "play only") analog device. Even with advances in wireless signal transmission, the prior art cone loudspeaker requires digital-to-analog converters in order to process input digital signals.
Further, prior art cone loudspeaker are not equipped to deal with multiple signal sources. The single function prior art cone loudspeaker cannot monitor its environment, receive and process multiple external signals, or act as a transmitter. In typical computer multimedia applications, sound signals may originate from a variety of sources such as a computer, compact disc (CD) player, telecommunications line or speech synthesizer. In order for these multiple signal sources to be used with a single prior art cone loudspeaker, the signals must currently be combined in a "mixer." Again, this approach involves the use of additional hardware components and inevitably degrades the sound quality.
Another problem with prior art cone loudspeakers is that the conical shape of the sound surface causes undesirable distortions in the creation, projection and propagation of sound waves from the loudspeaker. FIG. 1D shows how a prior art cone loudspeaker, having a voice coil assembly 30 and cone 32, propagates sound to a point in front of the speaker cone. Beyond this point, the acoustical energy is dispersed. Further, since the surface of the cone is non-planar, the wavefronts generated at different points on the surface of the cone produce a non-linear set of sound waves. In order to alleviate this problem, the prior art uses specially designed enclosures or cabinets to house the cone loudspeakers and attempt to baffle and redirect the acoustical energies to make the sound wave propagation more linear.
Finally, FIG. 1E illustrates another problem with the manufacture of prior art cone loudspeakers. FIG. 1E shows voice coil wires 12 adjacent to voice coil former 10 in a cross-sectional view. Note that, because of the geometric packing limitations of circular objects, voice coil wires can only achieve a limited volume coverage due to the necessary gaps between different windings of the wire. While some prior art coils use rectangular extruded wire to overcome such gaps, this extruded rectangular wire creates manufacturing difficulties. Many of these manufacturing difficulties are attributable to the process costs of extruding the wire in rectangular form and then winding the wire around the voice coil former. The process of extruding wire requires forcing metal at high pressure through an extrusion die. When a sharp edged rectangular wire is created, the high pressure and abrasion of this process causes the die to wear out quickly. Moreover, the process of winding the wire around a voice coil former can be an intricate operation where the rectangular wire is fine and the number of windings are many. Accurate winding is critical where rectangular wire is used because of the wire's sharp edges. Special care must be taken so that the rectangular wire does not twist while it is being wound around the voice coil former. If the rectangular wire twists, even slightly, there is the danger that a sharp edge will cut through the thin insulation surrounding the wire and cause a short in the coil. This problem is all the more troublesome because the short may not actually take place until after the coiled wire has been tested and placed into a service environment where added stresses due to operation, such as heat, bring about a short circuit.
In view of the these disadvantages with prior art cone loudspeakers, it is desirable to produce a loudspeaker that overcomes these disadvantages.